Steering gear housing for a steering unit in a vehicle

ABSTRACT

A steering housing for a steering unit in a vehicle has a housing tube for accommodating a linkage part, reinforcing struts being arranged at the exterior of the housing tube. Two reinforcing struts are respectively arranged adjacent to the two opposite ends of the housing tube and extend in different radial directions, wherein two reinforcing struts, respectively arranged at opposite ends of the housing tube are each bounded by one limiting plane, which lies at an angle to a tube axis through the housing tube.

This is a Continuation of PCT/EP2011/059456 Filed Jun. 8, 2011.

BACKGROUND OF THE INVENTION

The invention relates to a steering gear housing for a steering unit ina vehicle.

Steering units for vehicles are known wherein, in order to assiststeering, an electric servomotor is provided, which supplies anassisting torque via the steering gear of the steering unit. Thesteering gear with the steering linkage is accommodated in a steeringhousing, which is, for example, made of aluminum, in order to reduce theweight. For stability reasons, reinforcing ribs or struts may bearranged at the exterior of a housing tube of the steering housing, inwhich a linkage part is accommodated. In order to achieve safety-relatedprescribed stiffnesses and strengths for components, in general, thereinforcing struts are generously dimensioned; but this is detrimentalin terms of the weight of the steering gear housing.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to develop a steering gearhousing for a steering unit in a vehicle, having a simple construction,and having high stiffness and reduced weight

The inventive steering gear housing is a component of a steering unit ina vehicle, such as a passenger car or a commercial vehicle, and has atleast one housing tube, which is intended to accommodate a linkage part.Reinforcing struts are provided at the exterior of the housing tube,which confer increased stiffness to the steering gear housing.Preferably, the steering gear housing is made from a light metal, suchas aluminum or magnesium, and can be produced by injection molding.However, plastic housings with injection molded reinforcing ribs orstruts of metal, and particularly of steel, are also contemplated.

According to the invention, two reinforcing struts are provided which,in relation to the linear housing tube, are respectively adjacent to thetwo opposite ends of the housing tube, extend in different radialdirections, and have an increasing radial extension as the distance fromthe axial center of the tube increases. Two opposite reinforcing strutsare respectively bounded by a common limiting plane, which passesthrough the housing tube at an angle, with respect to a central plane.At least two reinforcing struts, which are angularly offset with respectto one another, are arranged at each end of the tube, wherein twoopposite reinforcing struts that are associated with each other arerespectively bounded by a common limiting plane. Accordingly, at leasttwo limiting planes exist, which, according to the invention, intersectat a location at the level of the housing tube.

The reinforcing struts, formed in this way, extend crosswise withrespect to the housing tube, which results in a significant increase instiffness, despite limited use of material. In each case, the tworeinforcing struts at opposite ends of the housing tube lie crosswise,such that the point of intersection of the limiting planes is at thelevel of the housing tube. Here, the point of intersection is within theexternal periphery of the housing tube, for example, at leastapproximately in the radial center of the housing tube.

In accordance with a further suitable embodiment, four reinforcingstruts, respectively extending in different radial directions, arearranged adjacent to the two opposite ends of the housing tube. In eachcase, the two opposite reinforcing struts are respectively arrangedcrosswise, bounded by a common limiting plane. Thus there is a total ofat least eight reinforcing struts, wherein each of the two mutuallyopposite reinforcing struts are bounded respectively by a commonlimiting plane. Consequently, it is possible to define four limitingplanes, wherein at least two limiting planes intersect at the level ofthe housing tube. Preferably, two of the four limiting planesrespectively intersect at a point level with the housing tube, theintersecting points of the respective two limiting planes notnecessarily coinciding with one another, even when this is possible.

By way of defining the limiting planes, an instrument is provided fordesigning the steering gear housing, allowing for high stiffness andstrength in the steering housing, with minimal material costs.

It may be appropriate to arrange the reinforcing struts, which arebounded by a common limiting plane and arranged on opposite sides of thehousing tube, offset to one another in the circumferential direction. Inprinciple, however, it is sufficient to arrange the reinforcing strutsat axially opposite ends, as well as on radially opposite sides, suchthat the planes, in which the two associated reinforcing struts lie,coincide. On the other hand, if the reinforcing struts are positionedoffset in the circumferential direction, the planes resulting from thereinforcing struts are either parallel or enclose an angle.

In a preferred embodiment, the reinforcing struts are constructed atleast approximately flat, but in principle curved or convexly orconcavely arcuate variations of the embodiment are also contemplated.Moreover, it is possible to construct the reinforcing struts with a wallthickness that changes over the axial and/or radial extension of thestruts. On the other hand, in accordance with a different embodiment, itis appropriate to provide a constant wall thickness either in the axialdirection or in the radial direction or in both directions.

In order to minimize material use, it is advantageous if a central axialsection of the housing tube is constructed either completely withoutreinforcing struts or formed in such a manner that the reinforcingstruts are reduced to a minimum in this section. For example, thereinforcing struts or ribs may have a constant radial height in thissection, which increases only in the transition to the reinforcingstruts at the end.

In terms of the steering unit, in particular, a steering system with aservo support, driven by an electric motor, is contemplated. Inprinciple, however, it is also possible to use the steering gear housingin steering systems with hydraulic servo support.

Moreover, it is possible to use the steering gear housing in an activesteering system, in which an additional steering angle can be produced,which can be superimposed on the steering angle specified by the driver.

Further advantages and appropriate embodiments are given in theadditional claims, the description of the figures and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a steering unit in a vehicle;

FIG. 2 shows a steering gear housing of the steering unit in a sideview;

FIG. 3 shows the steering gear housing in a representation rotatedthrough 90°; and

FIGS. 4 to 6 show the steering gear housing in different perspectiveviews.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the Figures, identical components are given identical referencenumbers.

The steering unit 1 comprises a steering wheel 2, a steering column orshaft 3, a steering housing 4 with a steering gear and a steeringlinkage 5 accommodated therein, by which a steering motion istransferred to the steerable wheels 6 of the vehicle. The driverspecifies a steering angle δ_(L) via the steering wheel 2, to which thesteering column 3 is firmly connected, and this is transferred by thesteering gear in the steering housing 4 to a rack-and-pinion system ofthe steering linkage 5, whereupon the steerable wheels 6 are set at asteering angle δ_(V).

In order to support the manual torque applied by the driver, an electricservomotor 7 is provided, by way of which an assistive servo-torque canbe provided to the steering gear in the steering gear housing 4. Insteadof an electric servomotor, a hydraulic assisting device may also beprovided, such as a hydraulic pump, which is driven by a combustionengine and supplies a hydraulic steering system.

In FIGS. 2 to 6 below, the steering gear housing 4 is shown individuallyin various aspects. The steering gear housing 4 comprises a hollowcylindrical housing tube 8 serving to accommodate a linkage part of thesteering linkage 5. The housing tube 8 of the steering gear housing 4,which is produced as an injection-molded aluminum part, has severalreinforcing struts or ribs 9 a, 9 b, 10 a, 10 b, 13 a, 13 b, 14 a and 14b, at the exterior, which are formed integrally with the housing tube 8and the steering gear housing, to which they confer increased stiffness.The reinforcing struts are provided adjacent to the respective ends ofthe housing tube 8 but may be at an axial distance from the respectiveend faces of the housing tube 8. The radial extensions of thereinforcing struts vary over the axial lengths thereof, increasing inthe direction of the end face of the housing tube. As can be seen, forexample, from the reinforcing struts 9 a, 10 a (FIG. 2) or 14 a, 13 b(FIG. 3), the outer edge of the reinforcing struts may be linear.However, it is also possible to have a convexly or concavely curvedouter edge, (reinforcing struts 13 a, 14 b, shown in FIG. 3) or an outeredge with alternating linear and curved sections, as shown, for example,for the reinforcing struts 9 b, 10 b in FIG. 2.

As can be inferred from the two views in FIGS. 2 and 3, which arerotated at an angle of 90° with respect to one another, four reinforcingstruts 9 a, 10 a 13 a, 14 a or 9 b, 10 b, 13 b, 14 b are respectivelyprovided at the two ends of the housing tube 8, the reinforcing strutsat one end of the housing tube being offset by approximately 90° fromone another. Each reinforcing strut in the region of a first end of thehousing tube 8 is associated with an opposite or diagonally crosswisereinforcing strut in the region of the second end of the housing tube.This results in pairs of reinforcing struts 9 a-9 b, 10 a-10 b, 13 a-13b and 14 a-14 b. The two respective reinforcing struts associated withone another in this manner are outwardly bounded by limiting planes 11,12, 15 and 16. Thus, the limiting plane 11 is associated with thereinforcing struts 9 a and 9 b, the limiting plane 12 is associated withthe reinforcing struts 10 a and 10 b, the limiting plane 15 isassociated with the reinforcing struts 13 a and 13 b, and the limitingplane 16 is associated with the reinforcing struts 14 a and 14 b. Here,the limiting planes 11 and 12 (FIG. 2) delimit the reinforcing strutpairs 9 a, 9 b, 10 a, 10 b, the reinforcing struts 9 a and 10 a or 9 band 10 b of which being arranged at one end of the housing tube 8, onopposite sides thereof. The same is true of the limiting planes 15 and16, which delimit mutually opposite reinforcing struts 13 a, 14 a and 13b, 14 b (FIG. 3) on respective sides of the housing tube 8.

Here, the two limiting planes 11 and 12 of the opposite reinforcingstruts form a point of intersection, which lies within the border of thehousing tube 8. Correspondingly, limiting planes 5 and 16, which areoffset by 90° with respect to the limiting planes 11 and 12, form apoint of intersection, which also lies within the border of the housingtube 8. In this context, the concept of “point of intersection” is to beunderstood in that the line of intersection, formed by the intersectinglimiting planes, passes through the housing tube 8 in the transversedirection, and accordingly, a section of the line of intersection,comprising a series of points of intersection, is present within thehousing tube 8.

The limiting planes enclose an angle with a tube axis 17 of the linearlyconstructed housing tube 8, which is at least approximately the same forall limiting planes 11, 12, 15, 16 and falls within an angular range ofnot more than 30° and more particularly of approximately 20°. The pointof intersection, or line of intersection, of two respectively mutuallyintersecting limiting planes 11, 12 or 15, 16 lies, at leastapproximately, on the axis 17 of the tube 8 or may optionally be shiftedslightly radially with respect to the axis 17 of the tube 8, as shown inFIG. 3.

LIST OF REFERENCE SYMBOLS

1 steering unit

2 steering wheel

3 steering shaft

4 steering gear housing

5 steering linkage

6 front wheel

7 electric servomotor

8 housing tube

9 a, 9 b reinforcing struts

10 a, 10 b reinforcing struts

11 limiting plane

12 limiting plane

13 a, 13 b reinforcing struts

14 a, 14 b reinforcing struts

15 limiting plane

16 limiting plane

17 tube axis

1. A steering gear housing for a steering unit in a vehicle comprising ahousing tube for accommodating a linkage part and having reinforcingstruts at the exterior of the housing tube wherein, adjacent to the twoopposite ends of the housing tube, at least two reinforcing strutsextending in different radial directions, are respectively arranged, andat least two reinforcing struts, respectively arranged at opposite endsof the housing tube, are each bounded by one limiting plane lying at anangle with respect to a tube axis through the housing tube, wherein atleast two limiting planes intersect at the level of the housing tube. 2.The steering gear housing according to claim 1, wherein adjacent to thetwo opposite ends of the housing tube, four reinforcing struts,respectively extend in different radial directions, are arranged, andtwo opposite reinforcing struts are respectively bounded by a commonlimiting plane.
 3. The steering gear housing according to claim 1,wherein the reinforcing struts bounded by a common limiting plane,arranged on opposite sides of the housing tube, are arranged offset toone another in the circumferential direction.
 4. The steering gearhousing according to claim 1, wherein the reinforcing struts have a wallthickness that varies over the lengths thereof.
 5. The steering gearhousing according to claim 1, wherein the reinforcing struts areconstructed at least approximately flat.
 6. The steering housingaccording to claim 5, wherein the mutually opposite reinforcing struts,bounded by a common limiting plane, lie in parallel planes.
 7. Thesteering gear housing according to claim 1, is constructed of a lightmetal, and particularly of aluminum.
 8. The steering gear housingaccording to claim 1, wherein the reinforcing struts are reduced to aminimum in a central section of the housing tube.
 9. The steering gearhousing according to claim 1, wherein the reinforcing struts have agreater radial extension as the distance from the axial center of thetube increases.
 10. A steering unit having a steering gear housingaccording to claim 1.